以下是一个示例代码，用于按频率筛选字符串列表：

from collections import Counter

def filter_by_frequency(strings, min_frequency):
    # 统计每个字符串出现的频率
    frequency = Counter(strings)
    
    # 筛选频率大于等于 min_frequency 的字符串
    filtered_strings = [string for string in strings if frequency[string] >= min_frequency]
    
    return filtered_strings

# 示例用法
strings = ['apple', 'banana', 'apple', 'cherry', 'banana', 'apple']
min_frequency = 2

filtered_strings = filter_by_frequency(strings, min_frequency)
print(filtered_strings)

运行上述代码的输出结果将是 ['apple', 'banana', 'apple']，因为字符串 'apple' 和 'banana' 的频率都大于等于 2。